1. Field of the Invention
The present invention relates to a video encoder for processing sequences of animated pictures, such as movies, and to a corresponding decoder.
2. Description of the Related Art
The MPEG-4 International Standard, described, for instance, in xe2x80x9cOverview of the MPEG-4 Version 1 Standardxe2x80x9d (document ISO/IEC JTC1/SC29/WG11 N1909, October 1997, Fribourg, Switzerland), is an object-based standard for multimedia. This means that the MPEG-4 standard is not only able to encode video pictures, as usually considered on a television screen, but it can also handle video data including shapes and textures within these shapes. The MPEG-4 video standard is, therefore, said to deal with YUVA input signals, YUV corresponding to the luminance and chrominance components, and A corresponding to what is called the A channel, or alpha channel.
An illustration of an YUVA object as encountered in the MPEG-4 standard is given in FIGS. 1 and 2, where FIG. 1 shows a colored picture corresponding to YUV signals and FIG. 2 shows only a shape, a contour between a black area and a white one. It is known, for instance, from the document xe2x80x9cRepresenting moving images with layersxe2x80x9d, by J. Y. A Wang and E. H. Adelson, IEEE Transactions on Image Processing, vol. 3, nxc2x05, September 1994, pp.625-638, that an alpha map -or an alpha plane- allows to define the transparency, or the opacity, of a region at each of its points, i.e., the shape of this region considered as transparent, while the remaining part is considered as masked, or obscured. The alpha plane may also be coded with 8 bits, which then allows a more precise information on the level of opacity or transparency of the object.
This functionality of dealing with YUVA signals gives the possibility to process each object of a picture in an autonomous way. The main application of said possibility is to implement a flexible management of the structure of video or audio-visual scenes, and of the composition of the elementary streams corresponding to said scenes, and more particularly, to compose scenes where data from different types can be managed independently.
It is an object of the invention to propose a new type of application of this functionality.
To this end, the invention relates to a video encoder provided for processing a sequence of animated pictures, such as a movie, said encoder comprising:
means for dividing a screen window occupied by said sequence into X rows and Y columns;
means for separately encoding each one of the Xxc2x7Y parts of each picture of the sequence thus obtained;
means for associating, to each of said parts a specific label indicating its position in the window, and encoding these labels in a random order.
The invention also relates to a corresponding video decoder provided for decoding input signals coded by means of this encoder, said decoder comprising:
means for decoding said encoded parts and said coded associated labels;
means for displaying the decoded parts thus obtained in a random order, while storing the decoded associated labels.
Said decoder preferably comprises post-processing means for displacing and reordering the displayed parts in the original correct order.
It is another object of the invention to implement a decoder in which said post( processing means comprises sets of computer-readable instructions allowing to play a puzzle and corresponding to the implementation of the following events:
displacement of a single displayed decoded piece of said puzzle from any location to any other one or to one of the Xxc2x7Y places available in a screen window corresponding to the reordered sequence of pictures;
displacement of a displayed decoded piece and all attached displayed decoded pieces from any location to any other one or to one of the Xxc2x7Y places available in said window.
Preferably, said:displacements are controlled by means of a mouse or a similar control device, with the following sequence of events xe2x80x9cLEFT BUTTON DOWNxe2x80x9d, xe2x80x9cMOUSE MOVExe2x80x9d, xe2x80x9cLEFT BUTTON UPxe2x80x9d for the displacement of any single piece, and with the following sequence of events xe2x80x9cRIGHT BUTTON DOWNxe2x80x9d, xe2x80x9cMOUSE MOVExe2x80x9d, xe2x80x9cRIGHT BUTTON UPxe2x80x9d for the displacement of any specific piece and all attached pieces.